Water continuous product stabilised with acetic acid

ABSTRACT

Chemically acidified water continuous products which have been acidified with a combination of a food grade acid and a small amount of acetic acid were found to be very stable against microbial spoilage.

FIELD OF THE INVENTION

The invention relates to water continuous products that are stableagainst microbiological spoilage, especially at a temperature below 20°C., preferably below 15° C.

BACKGROUND OF THE INVENTION

Water continuous products such as oil in water emulsions are prone tomicrobial spoilage on storage. Among these products are dressings,mayonnaise, fresh cheese, creamy spreads such as those disclosed inWO-A-97/08956 and quark type of products.

For each of these products measures are taken to ensure that they have asuitable shelf life when closed and also to ensure that they are notspoiled immediately after storage but can safely be consumed for sometime after opening. One of the bacteria causing spoilage after theproduct has been opened are those belonging to the family ofEnterobacteriaceae. These bacteria are also relevant in relation toproduct safety. Another group of bacteria which are preferably absent inproducts are Listeria.

For microbial preservation many of the above products rely on apreservation system which is a combination of heating (e.g.pasteurisation, sterilisation) and acid level (pH) to kill anyvegetative cells present in the product and to inhibit bacterial spores.Heating is in many cases sufficient to ensure closed shelf lifeprevented products are hermetically sealed after packing. Acid level ise.g. used in dressings where generally the level of acetic acid is about0.1 to 2 wt % on product weight.

U.S. Pat. No. 6,387,427 for example discloses a method of preserving afood product by adding a fermentate comprising acetic acid and/or itssalts resulting from the fermentation by acetic acid producing bacteriawhile the pH is maintained below 5.8. Although such products may bestable, the production of the fermentate by microbial acidification istime consuming and also the composition of the fermentate may varydepending on the exact conditions of microbial acidification, which aredifficult to control very accurately. Furthermore the acetic acid levelsare such that for many products an undesired acetic taste and flavourmay be present.

Furthermore e.g. products disclosed in WO-A-97/08956 which have beenprepared by microbial acidification may be stable but they again requirea step wherein microbial acidification is applied which is in some casesundesired. Microbial acidification may take long and makes exact processcontrol of e.g. the pH difficult.

Although it is known from the art that microbial acidification may bereplaced by chemical acidification, we found that this does not alwayslead to products with the desired microbial stability. For instanceproducts wherein an acidic pH is obtained by the mere addition of citricacid were found to spoil relatively easily, especially once openedunless they contain very high amounts of citric acid.

Therefore it is an object of the invention to provide chemicallyacidified products that are microbiologically stable on storage.

Especially preferred the products are essentially free ofEnterobacteriaceae and Listeria.

SUMMARY OF THE INVENTION

We suprisingly found that a combination of a food grade acid with a verysmall amount of acetic acid gives highly improved microbiologicalstability for water continuous products.

Therefore the invention relates to a water continuous, chemicallyacidified product comprising a fat, from 0.1 to 15 wt % protein, acids,and having a pH from 3.5 to 5.5 wherein the acids comprise a combinationof at least one food grade acid in an amount of from 0.01 to 2 wt % andfrom 10 to 1000 ppm acetic acid, on the weight of the product.

DETAILED DESCRIPTION OF THE INVENTION

In the context of the invention, the terms “fat” and “oil” are usedinterchangeably. The term oil encompasses both triglyceride oils anddiglyceride oils. Where the term fat is used also fat replacers such assucrose polyesters are encompassed.

For the purpose of the current invention, wt % is defined as weightpercent on total product weight unless otherwise is indicated.

Where the weight amount of an acid is referred to, the amount iscalculated in terms of the total amount of dissociated and undissociatedacid, unless otherwise is indicated.

The products according to the invention are chemically acidified. Thismeans that the desired acidic pH is obtained by the addition of (foodgrade) acids, contrary to the other method of acidification which ismicrobial acidification. Therefore preferred products are essentiallyfree from bacteria which are suitable for microbial acidification (whichis also referred to as fermentation). Examples of such bacteria arelactic acid bacteria, cheese starter cultures, yoghurt cultures, aceticacid producing bacteria. The presence of such bacteria (alive or deadafter a heat treatment) may be demonstrated by any suitable techniquesuch as ribosomal RNA identification with fluorescent oligonucleotidesor PCR of DNA.

The products according to the invention comprise a continuous aqueousphase. The dispersed phase is preferably fat or oil or a replacerthereof. Preferred products are spreadable, liquid and spoonableemulsions such as fresh cheese, spreads, low fat spreads, sauces,creams, drinks, acidified drinks, acidified milk, mousses, desserts,dairy spreads.

The products comprise a protein in an amount from 0.1 to 15 wt %.Especially products with protein present in the aqueous phase were foundto be prone to microbial spoilage and hence will benefit from theinvention because proteins are a well known source of energy forbacteria to grow on.

The products are acidified to a pH of from 3.5 to 5.5. The watercontinuous products preferably have a pH from 3.8 to 5.2, morepreferably from 4 to 5.2, more preferred from 4.2 to 5.2, even morepreferred 4.2 to 4.9.

The desired pH is obtained by the addition of a combination of at leastone food grade acid in an amount from 0.01 to 2 wt % and from 10 to 1000ppm acetic acid.

The preferred amount of food grade acid is from 0.1 to 1.2 wt %, morepreferred from 0.2 to 0.7 wt %. The skilled person will appreciate thatthe amount of acid added is linked to the desired pH of the finalproduct and the strength of the particular acid.

It is well known that microbiologically produced acids duringfermentation impart a specific, pleasant taste to food products.Therefore in a preferred embodiment, the food grade acid is composed ofacids that are formed during fermentation.

The food grade acid is preferably selected from the group comprisingcitric acid, lactic acid, hydrocholoric acid, benzoic acid, propionicacid, fumaric acid or a combination thereof. Also derived forms of thesesuch as their salts are encompassed within the invention. Maleic acid isless preferred.

The most preferred food grade acid is citric acid or a combination ofcitric acid and lactic acid. In preferred products the total amount oflactic acid is preferably below 0.5 wt %, for taste reasons.

The amount of citric acid is preferably from 0.1 to 0.8 wt %, morepreferred from 0.2 to 0.4 wt % on total product weight.

It was surprisingly found that the addition of only a small amount ofacetic acid showed a very good improvement in inhibition of microbialgrowth, especially of bacteria of the species Enterobacteriaceae. In apreferred embodiment the amount of acetic acid on total product weightis from 50 to 500 ppm, more preferred from 50 to 300 ppm, even morepreferred from 100 to 300 ppm, most preferred from 150 to 250 ppm.

In an even more preferred embodiment, the amount of undissociated aceticacid is controlled such that it is at least 75 ppm, more preferred atleast 80 ppm, even more preferred at least 100 ppm, even more preferredat least 150 ppm.

The higher levels of over 100 ppm undissociated acid are especiallysuitable to target stability against Listeria. The levels ofundissociated acetic acid from 75 ppm up to about 250 ppm are preferredto specifically target Enterobacteriaceae.

The invention is for example applicable to products which are of acreamy spread type. In such products the level of acetic acid ispreferably below 500 ppm to avoid a strong acetic taste for theseproducts. For other products such as dressings the amount of acetic acidmay be a bit higher because such products are usually characterised byan acetic acid taste and flavour.

In an even more preferred embodiment, the product comprises citric acidin an amount of from 0.2 to 0.4 wt % and acetic acid in amount from 100to 300 ppm on total product weight, preferably 80-200 ppm undissociatedacetic acid on total product weight.

The products preferably are water continuous products comprising from 1to 40 wt % vegetable fat, 0.5 to 10 wt % milk protein and 0.01 to 3 wt %thickener, having a pH from 4.2 to 5.5. These products are nutritionallybalanced and hence preferably comprise essential nutrients while theyare low fat.

The products according to the invention comprise a fat or a fatreplacer. Most preferred products are emulsions of a continuous aqueousphase and a dispersed fat phase.

The fat or fat replacer is preferably present in an amount of from 5 to90 wt %, more preferred from 5 to 70 wt %, more preferred from 5 to 50wt %, even more preferred from 10 to 40 wt %, most preferred from 15 to35 wt %. The invention is especially beneficial for products with a highamount of aqueous phase such as those where the amount of fat is below60 wt %. Such products are therefore preferred.

Although any suitable fats such as dairy fat, vegetable fat and fish oilmay be used, the preferred fat is vegetable fat. The vegetable fat ispreferably a fat rich in polyunsaturated fatty acids. Most preferred thefat is selected from the group comprising palmkernel oil, olive oil,soybean oil, rapeseed oil, coconut oil, sunflower oil, safflower oil, orfully or partially hardened fractions thereof. In a further preferredembodiment, the total amount of saturated fatty acid components in thefat is less than 45 wt %, based on the total amount of fatty acidcomponents, and further preferred less than about 30 wt %.

The products comprise a protein. The protein may be any protein such asmilk protein, soy protein, pea protein, meat protein. Preferred productscomprise from 0.5 to 10 wt % protein, preferably from 1.5 to 10 wt %,more preferred from 2 to 5 wt % protein.

Preferably the protein is milk protein and even more preferred the milkprotein is derived from the group comprising cream, milk, skim milk,butter milk, whey, casein or their powders or a combination of any ofthese. The most preferred milk protein source is skim milk powder.

The preferred amount of milk protein is from 2 to 6 wt %, more preferredfrom 2.5 to 4.5 wt %.

Although the invention is applicable for water continuous products ofany kind of texture, it is especially preferred that products arespreadable.

Therefore in a preferred embodiment the invention relates to productsthat are plastic, spreadable products, which can be applied onto breadat room temperature without tearing the bread. The products of thepresent invention preferably have a Stevens value of 100-500 g at 10° C.and 25-250 g at room temperature (about 20° C.), more preferred 150-450g at 10° C. and 25-200 g at room temperature (about 20° C.). The methodto determine Stevens value hardness is described in the examples.

To obtain the desired consistency and spreadable characteristics, theproducts according to the invention optionally comprise a thickener. Thethickener is preferably a biopolymer selected from the group comprisinglocust bean gum guar gum, tara gum, amylopectin, methylcellulose,alginate, starch, modified starch, high molecular weight pectin, gelatinor combinations thereof.

The preferred amount of thickener is from 0.1 to 3 wt %, more preferredfrom 0.3 to 2 wt %.

Optionally the product further comprises an ingredient selected from thegroup comprising vitamins, anti-oxidants, flavouring agent, egg yolk,gelatin, salt, metal ions such as calcium, potassium or a combinationthereof.

Although the acid combination according to the invention has a goodcontribution to improving the microbial stability of water continuousproducts against spoilage by especially Enterobacteriaceae, furtheringredients are optionally introduced to specifically provide protectionagainst other bacteria. An example of a suitable other anti-microbialagent that is optionally included in the product is potassium sorbate.

The products according to the invention are microbiologically stable.The microbial stability may be determined by the test described in theexamples.

The product may be prepared in any suitable way. A suitable process isfor example disclosed in WO-A-97/08956. It is preferred that the productis filled into a container at a temperature from 60 to 80° C. whereafterthe container is stored at a temperature below 10° C. More preferred thefilling temperature is from 65 to 75° C.

The invention is illustrated in the following non-limiting examples.

EXAMPLES

Stevens Hardness

The firmness of the products is determined by measuring the forcerequired to penetrate a cylindrical probe in the product. Sample height5 cm; cylindrical probe of 0.5 inch thickness; compression rate 2 mm/s;penetration depth 20 mm. The samples are stored for 7 days at 5° C., andstored at 10 or 20° C. for 4 h before the firmness measurement.

Microbial Stability Test

The microbiological stability of the products is determined using a“challenge” test which is a common test in the determination ofmicrobiological stability.

The test was carried out as follows.

Products were opened and a cocktail of strains of the Enterobacteriaceaefamily was added. Products were incubated at 10, 15 and 25° C. forseveral days. The amount of growth of Enterobacteriaceae was determinedby plating decimal dilution series of the “infected” products on agarplates. The plates were incubated at 30° C. for 2 to 5 days after whichthe numbers of grown colonies were counted. Typically forEnterobacteriaceae the increase of the number of colonies was determinedversus time.

Example 1

TABLE 1 Compositions Wt % on Ingredient product Fat (sunflower oil) 22Skim Milk Powder 6.25 Whey protein concentrate 1.75 (Nutrilac) LocustBean Gum (LBG) 0.3 Gelatin 0.7 Salt 0.3 Citric acid 0.35 (added as apowder) Acetic acid 200 ppm (added as 100% liquid) Carotene stock  4 ppmsolution, 1% in oil Demineralised water Up to 100%

Comparative example C1: same ingredients except that there was no aceticacid.

Process:

Water phase and fat phase ingredients except for acids were mixed atabout 60° C. After mixing the composition was pasteurized at 85° C. for10 minutes, and cooled down to 44° C., after which homogenisation at 200bar took place. To the homogenized composition acid was added asindicated, where needed hydrochloric acid was added until a pH of about4.7 or 4.5 was reached. This was followed by heating the mixture to 85°C. The obtained product was homogenized at 300 bar, and subsequentlyheated to a temperature of 75° C. for filling containers. The productwas filled into the containers. The container was stored below 10° C.

The product was presented to a panel of consumers. The products wereeasily spreadable. All confirmed that both products had a pleasantmouthfeel and taste and did not have an acetic acid off taste.

The results of the microbial stability tests were:

The samples with acetic acid (according to the invention) did not showany increase of colonies of Enterobacteriaceae over time. After about 10days at 10° C., even a reduction in the initial number of colonies wasobserved at pH 4.7.

For products at pH 4.7 without acetic acid (comparative example) growthof Enterobacteriaceae started between about 3 to 7 days storage at 10°C. After about 10 days the amount of colonies had increased about10-fold.

For products at pH 4.5 without acetic acid, the growth of colonies wasdeferred but was observed to start after storage for 10 to 14 days at10° C.

This confirms that the addition of a small amount of acetic acidinhibits microbial growth of Enterobacteriaceae. Therefore such productshave a longer open shelf life.

1. Water continuous, chemically acidified product comprising a fat, from0.1 to 15 wt % protein, acids, and having a pH from 3.5 to 5.5characterised in that the acids comprise a combination of at least onefood grade acid in an amount of from 0.01 to 2 wt % and from 10 to 500ppm acetic acid, on the weight of the product.
 2. Water continuousproduct according to claim 1 wherein the food grade acid is selectedfrom the group comprising citric acid, lactic acid, hydrochloric acid,benzoic acid, propionic acid or a combination thereof.
 3. Watercontinuous product according to claim 2 wherein the food grade acid iscitric acid or a combination of citric acid and lactic acid.
 4. Watercontinuous product according to claim 1 with a pH from 3.8 to 5.2, morepreferred from 4.2 to 4.9.
 5. Water continuous product according toclaim 1, which comprises from 5 to 90 wt % oil.
 6. Water continuousproduct according to claim 1 which comprises citric acid in an amount offrom 0.2 to 0.4 wt % and acetic acid in amount from 100 to 300 ppm ontotal product weight.
 7. Water continuous product according to claim 1wherein the amount of fat is from 1 to 40 wt % fat, said product furthercomprising 0.5 to 10 wt % milk protein and 0.01 to 3 wt % thickener andhaving a pH from 4.2 to 5.5.
 8. Water continuous product according toclaim 1, wherein the amount of lactic acid is below 0.5 wt % on totalproduct weight.